Electrical control system for presses



April 28, 1942. w. ERNST S ELECTRICAL CONTROL SYSTEM FOR PRESSES Filed Aug. 6l, 1939 atente@ acercas amorcer, courses. sacem/r son recesses Waiter Ernst, Mount Gilead, mno, asser to The llyuiic Development Corp. Enc., Wil- Warrington, nei., a corporation ci melaware apaisante accesi si, rasa vsensi No. seater v (ci. sante) t @laines This invention relates to electrical control systems for hydraulic machinery, and especially i or presses.

One object of this invention is to provide an electrical control system for hydraulic machin-v ery, such as presses, wherein the control switch assembly is simplined so that the same electrical units perform the functions of selecting the circuits and of initiating the energization of the circuits.

Another object is to provide an electrical control system for presses, wherein the system is controlled by push-button switches which may be locked in either of two opposite positions so that. a given push-button, switch serves not only as a momentary-action switch but also as a selector switch, thereby providing a system wherein one switch performs the functions previously performed by two switches.

Another object is to provide an electrical control system for hydraulic machinery, such as presses, wherein 'the source of pressure iiuid is number of switches and circuits required, and.

thus to simplify the control system.

In the drawing:

Figure l is a perspective view in front elevation of a commercial form of press embodying the electrical control system of this invention.

Figure 2 is a wiring diagram showing the electrical control system 'of this invention.

Figure 3 is a diagrammatic view, partly in section, showing one form of combined pushbutton and selector switch.

In general, the electrical control system of this invention consists of a solenoid which controls the direction of distribution of pressure uid to the press cylinders, this solenoid .being under the control of a magnetic contactor. VThe magnetic contactor, in turn, is under the control of a plurality of switches, two of which are combined push-button and selector switches. One such combined switch serves as a starting switch for forward operation, and also as a selector switch for semi-automatic or full automatic opa' eration. The other combined switch serves likewise as a push-button switch or as a selector switch for automatic operation or hand operation, in the latter instance rendering the electrical control system temporarily inoperative.

' failure thereof.

The combined switch itself is, in edect, a singlepole Vdouble-throw push-button switch, which normally rests in a neutral position between its two sets of poles, but which may be moved into engagement with the poles either momentarily or for a greater length of time by means of a locking device.

operating positions.

Referring to the drawing in detail, Figure l shows a hydraulic press embodying the electrical control system of this invention, Aand consists of a housing I containing a bed il, only a portion of which is visible. Rising from the bed ii are side members I2 forming housings concealing the strain rods I3, and push-back cylinders it having plungers i5 connected to the press platen I6 for returning the. latter to its retracted position as shown in Figure 1. The platen i@ is connected to the main plunger il, which reciprocates in the main cylinder i8, only the lower' end of which is visible. The main cylinder it is mounted on the press head I9, which is connected to the upper ends of the strain rods I3 and to the press side member i2. v

A The press head I9 is surmounted by a fluid tank or surge tank having a gauge 2| thereon for indicating the level of fluid inthe tank. The press head I9 also is provided with a shelf 22 which serves to support a. housing 23, within which are mounted the 'motor and pump for supplying pressure fluid to the main cylinder I8 and push-back cylinders I4. The lower housing I0 is provided Vwith a closure or removable door 24, permitting access to be had to the parts concealed by the housing I 0. A hand lever 25, mounted upon the shaft 26, provides for manual control of the press when the electrical control system is deenergized, or in the event of the ments of Figure 1 are described below in connection with the wiring diagram.

The electrical system shown in4 Figure 2 consists of the electric motor 30, connected by the lines 3l, 32 and 33 to the magnetic motor starting switch, generally designated 34, and consisting of an armature carrying switch blades 36, 31 and 38 and provided with an energizing coil 40. The blades 38, 31 and 38 are connected, respectively, to the branch power lines B, 4I and 42 leading to the main power lines 43, 44 and 45, respectively. The switch blade 39 forms an interlock or holding switch for maintaining the energization of the coil 40 when the normally Open motor starting push-button switch 41 is This locking device locks the push-button switch in at least one of its two The remaining electrical elereleased after being momentarily depressed to start the motor.

The push-button switch 41 is connected to the opposite poles of the switch blade 39 by the lines 48 and 49, respectively, the line 48 continuing to a `iunction with the branch power line 4|. The coil 40 is connected at one end, by the line 59,

-to the branch power line 42 and at its other end,

by the line to one pole of the normally closed motor stop push-button switch 52, the opposite end of which is connected to an extension of the line 49 beyond the normally open motor starting push-button switch 41. In this manner the starting and stopping of the pump-operating motor are under the control of the two pushf button switches 41 and 52.

The distribution of pressure fluidi. from the pump to the main cylinder |8 and push-back cylinders |4 is under the control of a solenoid 53. The latter may either shift a reversing valve, as in an open circuit, or reverse the shift ring of a reversible variable delivery pump, as in a closed circuit. In either case the energization of the solenoid 53 is under the control of the magnetic contactor, generally designated 54, and having a windingor operating coil 55, an armature 56 and switch blades 51, 58 and 59.. The switch blades 51 and 58 directly control the energization of the solenoid 53 from the branch power lines 68 and 6|, whereas the switch blade the oil temperature limit switch 65, the platen-V operated auxiliary start limit switch 86 and the forward push-button switch 61. control switch 64 is a normally closed springloaded switch having a pressure plunger which 'I'he tonnage 11'?.

at a predetermined pressure overcomes 'the thrust of the spring and opens' the switch to break the circuit. The oil temperature limit switch 65 is a normally closed switch, actuated by a thermostat at a predetermined temperature to stop automatic operation when the oil temperature reaches a maximum limit. The platenoperated auxiliary start limit switch 66 is a normally open limit switch which is automatically closed when theplaten nears the end of its return stroke so as to automatically restart the platen upon another forward stroke, and thereby to eiect full automatic operation. The forward push-button switch 61 is merely an additional precaution to require the use of the other hand of the operator which is not required in manipulating the push-button switch 62 for safety pur poses.

The switches 62 to 61 are interconnected by an electrical circuit with the magnetic contacter 54. A "semi-automatic pole of the switch 62 is connected by the line 68 to a pole of the forward push-button switch 61, from the opposite pole of which the line 69 runs to one pole of the limit switch 66. From the opposite pole of the latter the line 10 runs to a full automatic pole of the switch 62. 'I'he other semi-automatic pole and full automatic pole are interconnected by the line 1|, which continues onward to one pole of the tonnage control switch 64. From the same pole the line 12 runs to one end of the operating coil 55 of the magnetic contacter 54, the other end of which is connected by the line 13 to'an automatic pole of the pushbut ton switch 63, the remaining automatic pole of which is connected by the line 14 to one pole of the oil temperature limit switch 65, the other pole of which is connected by the line 15 to the branch power line 6|. The remaining pole of the tonnage control switch or pressure-responsive switch 64 is connected by the line 16 to one pole of the interlock blade 59 ofV the magnetic contacter 54, the opposite pole of which is connected by the line 11 to the branch power line 68, and by the line 18 to one pole of the forward push-button switch 61.

In order to indicate when the automatic circuit is in operation, there is provided a pilot light 19, connected on. the one side by the line 88 to one pole of the switch 63 and o'n the other side by the line -8| to one pole of the magnetic contacter interlock blade 59. The line 8| optionally contains a resistance 82, depending upon the characteristics of the pilot light 19.

The combined push-buttonl and. selector switches 82 and 63 may be of any suitable type, one type being indicated diagrammatically in Figure 3. This switch consists of a plunger 83 carrying a push-button 84 and a switch blade 85, with contact points 86. The plunger 83 is also provided with a collar 81 engaged by a coil spring 88, which abuts against the rear switch housing wall 89, Surrounding the plunger 83 is a rotatable sleeve 90 of approximately cylindrical form, having an annular portion 9| projecting from the front panel of the switch housing 89 and having a grooved portion 92 loosely engaging the latter. The annular portion 9| is preferably knurled so as to be easily engageable by the ngers of the operator. Y

Connected to the sleeve 90, as by the bolts 93. is acylindrical cam 94 having a cam surface 95 engaging a pin 96 mounted upon the plunger 83. Mounted adjacent the raised position of the switch blade are spaced pairs of switch poles 91 and 98, respectively; By pushing the pushbutton 84 the switch blade 85 may be caused to engage the poles 98, whereas a motion of the plunger 83 in the opposite direction causes the switch blade 85 to engage the poles 91 when the sleeve 90 is so rotated that the pin 96 engages the lower portion of tlie cam surface 95. The switch blade 85 may be locked midway between the contact points 91, 91 and 98, 98 by rotating the annular portion 9| with the sleeve 98 so that the pin 96 rides up onto the high part of the cam 94.

In the operation of the circuit shown in Figure 2. the motor 38 is started by momentarily depressing the motor starting push-button switch 41. This energizes the operating coil 49 of the magnetic contactor 34, and the energization is maintained by a holding circuit established through the line 49, the interlock switch blade 39 and the line 4|. These bridge the push-button switch 41 when it is released. The motor may be stopped at any time by depressing the normally closed push-button switch 52, thereby halting the pump which supplies pressure fluid to the main cylinder |8 and .pushback cylinders I4.

If the operator decides to employ hand-operation by using the hand lever 25, he depresses the combined push-button and selector switch 63 and locks it by rotating the annular portion 9|. so that the circuit is broken between the lines 13 and 14. The electrical control circuit is then deenergized and the press is controlled directly by means of the hand lever 2.5, thereby directly moving the control rod of the press and the main control valve, or the pump shift ring, as the case l may be. To chan'ge from hand operation to semi-automatic operation, the switch 53 is returned to its upper automatic operation position, and the operator then depresses the forward vstarting push-button 81, and moves the combined push-button 62 until it engages thesemi-automatic contacts. If he desires semiautomatic operation, whereby the platen" it executes a forward stroke, halts, executes a return stroke and then halts at the end of its return stroke, no further attention is required on the part of the operator.

button and selector switch 63, the line ed, the

line 16, switch blade 59 and line 11, to the branch power line ci). The solenoid 53 is then directly energized through the switch blades 5l and 5E,

and operates upon the main control valve or the pump shift ring to deliver pressure fluid to the top of the main cylinder I8. and bring about a forward stroke of the main plunger I1 and platen it.

When the platen I6 has advanced and performed work upon the workpiece, the consequent rise in pressure opens the tonnage control switch 64 when its set pressure is exceeded. This breaks the energization circuit of the magnetic contactor coil 55 between the lines 12 and 16 and causes the magnetic contactor N to open,

thereby deenergizing thesolenoid 53. The usual 1:

springs will then return the main'control valve or pump shift ring to the reversed delivery position so that pressure uid is supplied to the push-back cylinders Il and withdrawn from the main cylinder i8. Under these circumstances the main plunger I1 and platen I6 will execute a return stroke. In a mechanical manner not shown in the drawing but known to those skilled in the art, the platen I6, at the endof its return stroke, directly shifts the main ,valve or shift ring of the pump to a neutral position. whereby no further pressure` fluid is delivered either to the push-back cylinders I4 or main cylinder I8. The main platen I6, therefore, halts automatically at the end of its return stroke and completes one cycle of semi-automatic operation.

If full automatic operation is desired, whereby the press platen l5 will perform a repeated number of forward and return strokes without halting more than momentarily at the end of each stroke, the operator depresses the push! button switches 62 and 61 as before to get the device started and then actuates the locking ring or annular portion 9| to bring the switch blade 85 to its dotted position designated full automatic," namely, the upper position in Figurez. The magnetic contactor '5t and solenoid 53 are energized, as follows: From the branch line @i current flows through the line 15, the oil ternperature limit switch 55, the line le, switch 53, and line 13 to the operating coil 5t. From here the current flows through lines 12, 1l and lil, the switch St, lines 69, 13, 1l and 6@ back through the line ed. As soon 'as the coil 55 is energized, the blades 5t, 5B and 5l form the circuits previously described in connection l with semi-automatic operation, switch te being bridged by the lines 6U and l?, blade 59, line le and switch til. .Consequently the' platen it executes a working stroke, is reversed automatically by the opening of the tonnage control pressureresponsive switch tt, and returns to its starting position. Instead of remaining at the end of its return stroke, as in semi-automatic operation, however, the platen it closes the switch et before it movesthe pump control or main valve to neutral. The closing of the limit switch Se in this manner `bridges the forward push-button switch 6l and effects starting energization between the lines 'H and l@ by way of the lines @t and 10 and. the now closed -limit switch t6.

Under these circumstances, the magnetic con-v tactor coil 55 is automatically reenergized and the consequent reenergization of the solenoid 53 again shifts the main valve or pump control to cause pressure fluid to be applied to the top ci th'e main cylinder I. Accordingly, the press platen IS immediately starts upon another forward or working stroke without halting more than momentarily at the end of its previous return stroke. The press will then proceed to execute a repeated number of cycles until theswitch 62 is released from its full automatic position, or until the oil temperature limit switch 65' is opened by a serious rise in temperature, or the motor stop push-button switch 52 is operated,'or until the operator depresses the switch t3.

Thus, in the `control circuit of the present invention, the combined push-button and selector switches 62 and 63 not only serve the functions of the ordinary push-button switches previously employed, but also serve to select the circuit for hand or automatic operation, and also for full automatic o semi-automatic operation. Thus,

by the ,present invention, two push-button switches previously considered necessary have been eliminated, namely, an additional forward push-button swltch'simllar to the forward pushbutton switch 61, and a normally closed reverse push-button switch similar to the motor stop push-button switch 52. Obviously, the operation of the entire circuit may be halted at any time by opening the motor stop switch 52.

It will be understood that I desire to comprehend withinthe .invention such modifications as come within the scope of the claims.

Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent, is:

l. In a hydraulic press control system, the combination with a' reversible hydraulic motor means having a reciprocable ram and a source of pressure fluid therefor with a flow-control member i'or reversibly controlling the distribution of pressure fluid to said hydraulic motor means, of an electric circuit comprising means including an Velectrical device for selectively shifting said nowcally altering the energization of said electrical device for initiating a. retraction stroke of said ram at the end of a ram-advancing stroke, means for automatically re-altering the energization of said electrical device at the end of a retraction stroke for eilecting an immediately repeated advancing stroke, a combined main starter and selector switch for effecting energization of said circuit and for selecting said immediately repeated advancing stroke, an auxiliary starter switch adapted to cooperate with said main starter and selector switch for starting energization of said circuit, and means for electrically connecting said last mentioned switch selectively with said auxiliary starter switch or said re-altering means. Y

2. In a hydraulic press control system, the combination with -reversible hydraulic motor means having a reciprocable ram and a source of pressure fluid therefor with a now-control member for reversibly controlling the distribution of pressure iiuid to said hydraulic motor means, of an electrical control circuit arranged to effect full automatic reversal of said flow-control member at the end of the advancing and retracting strokes of said ram, said circuit including a combined starter andselector switch movable selectively from a neutral position into one of two operative positions, circuit means adapted to be closed by said combined switch in one of its operative positions for starting operation of said hydraulic motor and conditioning the same for semi-automatic operation, and circuit means adapted to be closed by said combined switch in its other operative position in cooperation with means operable at the end of a retraction stroke of said motor.

3. In a hydraulic press control system, the

combination with reversible hydraulic motorI means having a reciprocable ram and a source of pressure fluid therefor with a now-control member for reversibly controlling the distribution Yof pressure fluid to said hydraulic motor means,

of an electrical control circuit arranged to effect full automatic reversal of said flow-control member at the end of the advancing and retracting strokes of said ram, said circuit including combined momentary and prolonged contact switch means for selectively effecting full automatic and semi-automatic energization of said circuit to selectively produce full automatic and semi-automatic operation of said ram respectively, said switch means including a push-button switch having a device for holding the same in a prolonged contact position. l

4. In a hydraulic press control system, .the combination with reversible hydraulic motor means having a reciprocable ram and a source of pressure fluid therefor with a now-control member for reversiby controlling the distribution of pressure fluid to said hydraulic motor means, of an electrical control circuit arranged to eiect full automatic reversal of said now-control member at the end of the advancing and retracting strokes of said ram, said circuit including combined momentaryA and prolonged contact switch means for selectively effecting full automatic and semi-automatic energization of said circuit to selectively produce full automatic and semi-automatic operation of said ram respectively, said switch means including a push-button switch having selective holding means engageable therewith for releasably holding said switch in a prolonged contact position.

5. In a hydraulic press control system, the combination with reversible hydraulic motor means having a reciprocable ram and a source of pressure iiuid therefor with a flow-control member for reversibly `controlling the distribution of pressure fluid to said hydraulic motor means, of an electrical control circuit arranged to effect full automatic reversal of said flow-control member at the end of the advancing and retracting strokes of said ram, said circuit including combined momentary and prolonged contact switch means for selectively effecting full automatic and semi-automatic energization of said circuitto selectively produce full automatic and semiautomatic operation o t said ram respectively, said switch means including a push-button switch movable selectively into -one of two contact-engaging positions and having holding means] for releasably holding said switch in a prolonged contact in one of said contact-engaging positions. l

6. In a hydraulic press control system, the combination with hydraulic motor means having a reciprocable ram and a source of pressure fluid with a flow-control member for reversibly controlling thedistribution of pressure fluid to said hydraulic motor means, of -an electrical control circuit arranged to selectively effectfull automaticand semi-automatic operation of said iiowcontrol member for producing full automatic and semi-automatic operation of said ram, said electrical circuit including a combined push-button and selector switch momentarily engageable and having a holding device for holding said switch in prolonged contact.

7. In a hydraulic press control system, the combination with hydraulic motor means having a reciprocable ram and a source of pressure iluid with a flow-control member for reversibly controlling the distribution of pressure` iluid to said hydraulic motor means, of an electrical control circuit arranged to selectively effect full automatic and semi-automatic operation of said flowcontrol member for producing full automatic and semi-automatic operation `of said ram, said electrical circuit including a combined push-button and selector switch momentarily engageable and having a holding device for holding said switch in prolonged contact, said switch having a neutral position of disengagement.

8. In a hydraulic press control system, the combination with hydraulic motor means having a reciprocable ram and a source of pressure uid with a now-control member for reversibly controlling the distribution of pressure iiuid to said hydraulic motor means, of an electrical control circuit arranged to selectively effect full automatic and semi-automatic operation of said flow-control lnember for producing full automatic and semi-automatic operation of said ram, said electrical circuit including a combined push-but ton and selector switch momentarily engageable and having a holding device for holding said switch in prolonged contact, said switch having a semi-automatic position of engagement, a fullautomatic position of engagement and a neutral position of disengagement therebetween.

WALTER ERNST. 

